Regular patient assessments between outpatient encounters could improve clinical decision-making, particularly when patients face access barriers. These assessments also could allow health care systems to measure the quality of services they deliver from a consumer perspective. We will examine variation in patient-centered outcomes for patients with diabetes using an automated telephone disease management (ATDM) system that conducts periodic assessments while patients are in the community. We will enroll 350 patients from a public health care system and 350 patients from a large private managed care system serving the same geographic region. Samples in each system of care will be divided equally between primarily English-speaking and Spanish-speaking patients, and we will enroll equal numbers of patients with primary providers who are specialists and general practitioners. We will develop ATDM assessment instruments that include measures of patients' glycemic control, self-care, health-related quality of life (HRQL), and satisfaction with care. These instruments will be based on widely-used scales with known psychometric properties and will be developed with input from a panel of experts in guidelines-supported diabetes care, the measurement of patient-centered outcomes, health care performance monitoring, and case mix adjustment. Patients will receive weekly ATDM assessments for one year, and other data will be collected via quarterly patient surveys, medical record reviews, glycosylated hemoglobin (HgA1c) testing, and electronic utilization databases. We will evaluate the reliability and validity of patients' ATDM reports using measures of consistency and the extent to which the data corroborate contemporaneous information collected using other methods. We will develop statistical models that measure the extent to which the ATDM reports improve the prediction of health outcomes (e.g., HgA1c) beyond what is possible when limited to data that is typically available to ambulatory care physicians. Finally, we will examine case mix-adjusted differences in ATDM-reported outcomes across systems of care and provider specialties and will explore the contribution of treatment processes to these differences. In summary, this study will determine whether an ATDM assessment system is a pragmatic strategy for monitoring the health of large panels of patients with diabetes and circumventing access barriers such as the absence of language-appropriate care. We also will use the assessments as a patient-centered method of measuring the quality of ambulatory care, a dimension of quality assessment that has been under-emphasized due to the difficulty and expense of gathering such information.